In ink jet printers, the physical distance between the ink jet pen and the paper or other media upon which the ink is being ejected, known as the pen-to-paper spacing (PPS), has a significant effect on the quality of the printing. If the PPS varies outside a relatively narrow tolerance range, depending upon the particular printer, the quality of printed images is noticeably affected. Careful control of the pen-to-paper spacing improves positioning of the ink drops, which in turn produces better images.
The pen-to-paper spacing in a printer can change throughout the printer's lifetime due to a variety of factors, such as paper jams, printer handling, servicing, pen changes, etc. Some ink jet printers, particularly lower cost models, are not designed to allow adjustment of the pen-to-paper spacing after the printer leaves the factory. With these printers, some slight variation in the PPS over time is expected, along with a corresponding variation in print quality.
Other printers, particularly high-end color photographic printers, are configured to allow the PPS to be checked and adjusted periodically. Some printers in this category are designed as photographic printers, and can print high-resolution digital photographs on high quality photographic paper. In order to maintain high quality printing, it is desirable that the uniformity of the PPS be accurately maintained in these printers. Under current methods, checking the uniformity of pen-to-paper spacing in an ink jet printer is a relatively complicated and time-consuming process. Checking the PPS takes a skilled technician several minutes using an expensive measuring tool that the technician has been trained to operate. Only after the spacing has been checked can the technician then make any necessary adjustments.